How to calculate pool volume
Rectangle: length × width × average depth
Round: 3.1416 × diameter² ÷ 4 × average depth
Oval: 3.1416 × length × width ÷ 4 × average depth
Litres = cubic metres × 1,000
For a kidney or freeform pool, split it into a rectangle and half circles, or use the oval shape with the longest length and the average width as a close estimate.
Salt for a salt water pool
Each 1,000 ppm in 10,000 litres needs 10 kg of salt.
Typical pool volumes
| Pool | Size and depth | Litres |
|---|---|---|
| Plunge pool | 4 × 2.5 m, 1.4 m average | 14,000 |
| Small backyard pool | 6 × 3 m, 1.4 m average | 25,200 |
| Family pool | 8 × 4 m, 1.4 m average | 44,800 |
| Large pool | 10 × 5 m, 1.5 m average | 75,000 |
| Round above-ground pool | 4.5 m diameter, 1.2 m deep | 19,085 |
Worked example
An 8 m × 4 m pool, 1 m deep at the shallow end and 1.8 m at the deep end, has an average depth of 1.4 m: 8 × 4 × 1.4 = 44.8 m³, or 44,800 litres. Bringing new water to 5,000 ppm takes 224 kg of salt, about 12 bags of 20 kg.
Running a pool pump? See what it costs with the electricity cost calculator.
Frequently asked questions
How many litres are in an 8 x 4 m pool?
About 44,800 litres with an average depth of 1.4 m.
How much salt does a salt water pool need?
For 5,000 ppm, about 5 kg per 1,000 litres of fresh water: 224 kg for a 44,800 litre pool.
How do I work out the average depth?
Add the shallow end and deep end depths and divide by 2. A pool 1 m to 1.8 m deep averages 1.4 m.
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Last updated October 2026.